With the growing demand of data traffic in wireless network, improving system throughput and spectral efficiency has become the focus of future wireless network access architecture.
Inter-base station interference coordination is a crucial technique to sufficiently achieve the potential capacity of a system. Particularly in the wireless network cloud environment with co-existence of multiple heterogeneous networks, it is of great importance for improving system spectrum efficiency to achieve interference coordination between different types of base stations. A long-term evolution (LTE) system, as an important quasi-4G system, uses overload indicator and high interference indicator (HII) to perform inter-cell interference coordination. After the LTE introduces a low-power node, it performs heterogeneous network interference coordination mainly by adopting the following three methods: multicarrier method, multicarrier-aggregation method, and co-channel method.
In the multicarrier method, different types of networks use different carriers. This method apparently wastes spectrum and is thus rather inefficient.
The multicarrier aggregation method usually reduces the interference between control channels through coordinating downlink control signaling of different cells to be transmitted over different frequency bands. In this way, a terminal supporting carrier aggregation has a higher throughput. However, it has no effect for a terminal not supporting carrier aggregation, for example, a R8 terminal. Thus, it has a poor compatibility.
Implementation of interference coordination in a co-channel condition mainly comprises time offset, almost blank subframes, and new control channel design. The time offset solution comprises OFDM symbol offset and subframe offset. The interference between control channels may be eliminated. However, the control channel and reference signals of the low-power nodes are still subjected to the interference from data channels of a macro cell, and this solution is not suitable for time division duplex (TDD) mode. The almost blank subframe solution refers to dividing all subframes of the system into regular subframes and almost blank subframes, wherein users of one network type do not send the control channel and data channel on an almost blank subframe, and users of another network type use that subframe to send the control channel and data channel. Although this solution solves the compatibility problem well, it still has relatively low resource utilization because in the almost blank subframes of a macro cell, the control information and data information of the macro cell still cannot be transmitted. Even if this solution becomes more flexible through semi-static adjustment with respect to dividing the almost blank subframes, such that the relatively low resource utilization is improved somewhat, however, the resource utilization of the system cannot be guaranteed yet due to the relatively long semi-static adjustment period.
A further solution is to design a new control channel. Because the control channel of a micro cell is subjected to the interference from a macro control channel, a new control channel may be introduced into a data subframe of the micro cell. The new control channel spans across the entire subframe temporally, but occupies less subcarriers in frequency domain. At this point, the new control channel will not be subjected to the interference from the macro cell and may flexibly use data resources of the micro cell. However, this solution needs to design a new control channel, which has a great influence on the standard.
Therefore, there is a need for a method for interference coordination that sufficiently enhances the spectral resource utilization and cell edge user's performance.